Gas chromatography

Hi
i do investigation in microbial ecology of hydrocarbon degrading bacteria.

All isolates i have degrading hydrocarbon are strictly aerobic. i wish to study the degradation kinetics (successive deplition of hydrocarbons in culture medium) of these bacterial strains. But, my doubt is hydrocarbons are volatile in nature, and when i start do the experiment i suspect the non-specific (colatilization) of hydrocarbons will mislead my results. and my bacteria are strictly aerobic (so, i cant plug with teflon lined stopper for culture flask).
so, some one related to this feild please let me know how to proceed